Improved sealing apparatus

ABSTRACT

The present invention provides a pressure control device ( 10 ) suitable to be mounted on a rigid mandrel or the like and to form a seal in an oilwell, for example, in order to deploy a zonal control system. The pressure control device comprises a flexible sealing element ( 18 ), a first support member ( 30, 32 ) and a second support member ( 34, 36 ). One of the support members ( 34, 36 ) comprises a composite material.

FIELD OF THE INVENTION

The present invention belongs to the field of oil and gas wells drillingand production of oil and gas from wells drilled on the earth. Moreparticularly it relates to the field of zonal isolation whereindifferent sections of an oil or gas well are sealingly isolated fromother well sections to avoid cross-contamination with fluids such aswater, undesired pressure transmission between sections or for otherreasons.

BACKGROUND TO THE INVENTION

In the oil and gas exploration and extraction industries it is oftendesirable to be able to modulate downhole pressure when required. Forexample, it may be desirable to isolate a section of well bore to createsections of differential pressure within the bore. A sealing device maybe used to create a seal within the bore, such that fluid pressure onone side of the seal increases relative to fluid pressure on the otherside. Further, a temporary decrease in well pressure can be used toinitiate flow from the reservoir in a process known as ‘swabbing’. Onemeans of doing this is to make use of a swab cup, which is a cup-shapedresilient member which is lowered on a mandrel into the well. As apressure differential develops across the cup, the walls of the cup arepushed into contact with the well tubing or bore wall, thereby sealing aportion of the well. Thus, the pressure below the cup may decrease,while the pressure above may increase.

Similarly constructed pressure cups are also used in a wide variety ofother sealing and fluid lifting applications. For example, variations inpressure may also be used to actuate or to control other downhole toolsand instruments which rely on fluid pressure for their operation. Suchcups may be constructed with an outer diameter slightly less than thebore diameter, such than an initial inflation is required before a sealis created, or may have an outer diameter slightly larger than that ofthe bore, such that a seal is present even when the cup is not inflated.

Alternatively, a pressure differential may be achieved by means of apacker. The sealing element on a packer is compressed and activated viaa setting load caused by mechanical or hydraulic or other forces. Theseare used to isolate different parts of the well for numerous downholeoperations, such as well testing or completions.

Conventional pressure seals suffer from a number of disadvantages. Theseals are usually made from rubber or other elastomer, which must bemade relatively thick in order to resist the pressures downhole. Thismeans that such seals may be unsuitable for use at relatively lowpressures, since they will not seal the well effectively under theseconditions. The relatively thick elastomer can also suffer from slowrecovery times after pressure has been removed. Seals may be reinforcedin order to resist higher pressures with metal or wire hoops or ringsembedded within the elastomer; however, this can lead to shear failureof the elastomer, with the reinforcing wire cutting through theelastomer.

In addition, conventional seals may only operate over a restricted rangeof pressures and temperatures, and with a small gap between the seal andthe bore wall. If the gap between the seal and the bore is increased,the pressure that the seal will hold drops considerably.

Further, elastomers under pressure can flow or extrude in certainconditions. This may arise in seals or packers, and will reduce theeffectiveness of such seals or packers, because elastomer flows orextrudes while the seal is under pressure. Any tendency to flow orextrude is also exacerbated at higher temperatures.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda pressure control device for mounting on a mandrel, the devicecomprising:

a flexible sealing element;

a first support member; and

a second support member comprising a composite,

wherein the pressure control device is adapted to move from a run inposition to an expanded position when exposed to a source of pressure,the flexible sealing element is adapted to form a seal against a borewall in the expanded position, the first and second support membersbeing adapted, in the expanded position, to resist extrusion of theflexible sealing element, in use, along the bore wall away from thesource of pressure, the second support member being further adapted toresist extrusion into the first support member.

In at least one embodiment of the present invention an apparatus asdescribed above is able to sealingly isolate two sections of an oil orgas well and at the same time maintain its integrity under wellborepressure differentials, thus preventing extrusion and deformation of theflexible sealing element and of the second support member and thereforemaintaining the seal leak-free. This invention is particularly suitableto achieve effective zonal isolation under extreme pressures andtemperatures, such as those encountered in high pressure, hightemperature wells (HPHT wells).

Furthermore, by provision of a second support member in the form of acomposite, extrusion into the first support member of flexible sealingelement material or second support member material is resisted, allowingfor greater recovery of the first support member, when the source ofpressure is released, towards the run in position.

The pressure control device may be a cup seal or a swab cup.

Alternatively, the pressure control device may be a packer or anysuitable pressure control device comprising a flexible sealing element.

A portion of the flexible sealing element, the first support memberand/or the second support member may be arranged concentrically.

The first support member may further comprise a circumferential spring.

The circumferential spring may be biased to the run-in position.

The first support member may be located at an outer portion of theflexible sealing element. Such an arrangement assists in recovery of theflexible sealing element from the expanded position to the run inposition, when source of pressure is reduced or eliminated.

In certain embodiments of the invention, the first support member mayalso be urged outwardly against the bore wall, in use, to help to createthe seal.

In at least one embodiment of the present invention the spring is ahelical spring.

In other embodiments the spring may be a garter spring.

In some embodiments the spring may comprise a first spring with a secondspring in its interior. The second spring may be mounted within thefirst spring such that the helix of one spring is wound in the oppositedirection to the spiral of the other spring in order to resist cantingof the first support member under high pressure. In some embodimentsthis arrangement of the springs also confers benefits for reducing theextrusion of the second support member into the first support member.

Alternative spring forms and/or arrangements may be used withoutdeparting from the principles of the invention.

The first support member may alternatively or additionally comprise apetal arrangement.

The petals may be overlapping. In moving from the run-in position to theexpanded position, the petals open up but still form a continuoussurface to resist extrusion of the flexible seal element along the borewall away from the source of pressure.

The first support member may be located so as to abut the second supportmember. Such an arrangement restricts movement of the first supportmember to some degree when the device is pressurised, and may be used todirect movement of the first support member to improve formation of aseal.

The pressure control device may comprise a rigid body adapted formounting on a mandrel or the like.

The rigid body may comprise an annular member.

The first support member may be mounted to the annular member.

The rigid body may comprise a cammed surface adapted to be engaged bythe first support member.

The cammed surface may be arranged to direct the first support memberradially outward when the device is under pressure. This may be achievedby the cammed surface being inclined axially downwardly from the centreof the device and radially outward. Such an arrangement also providesfurther integrity of sealing by ensuring the first support member has toovercome both the pressure within the pressure control device and thedirection of the cammed surface to return to the run-in position.

Alternatively, the cammed surface may be inclined upwardly, or may begenerally horizontal; these arrangements may be used to delay orrestrain expansion of the first support member and/or flexible sealingelement, which may be useful in certain applications.

The first support member may be bonded to the second support member.

In alternative embodiments the first support member may be located on oradjacent the second support member.

In at least one embodiment of the present invention the second supportmember comprises a composite of greater hardness than the flexiblesealing element located at an outer portion of the flexible sealingelement. When the composite portion is of greater hardness than theflexible sealing element itself, it will be less susceptible to flow orextrusion due to the pressure, so improving effectiveness of the device.This feature also allows the flexible sealing element to be made ofsomewhat thinner or less hard material than in previous devices.

The composite of the second support member may comprise a compositematrix and a reinforcing material.

The reinforcing material may be more rigid than the composite matrixmaterial. In at least one embodiment of the present invention thereinforcing material adds rigidity to the second support member andimproves its anti-extrusion properties at high pressures. This is ofbenefit because when in use, it will resist extrusion into the firstsupport member and therefore it will not hamper the recovery of the cupor packer original size and shape upon removal or reduction of deformingpressure.

In at least one embodiment of the present invention the reinforcingmaterial may comprise a plurality of separate members, particles orfibres.

In other embodiments the reinforcing material may comprise at least oneaggregated member. In at least one embodiment of the present inventionone or more aggregated members provide(s) enhanced anti-extrusionproperties to the second support member and also helps resist better theextrusion of the flexible sealing element by providing better tensilestrength.

The/each aggregated member may comprise a mesh.

The mesh may comprise metal wire. Other semi-rigid materials may be usedfor the mesh without departing from the principles of the invention.Metal wire meshes are easily available at affordable prices and providethe required mechanical and anti-extrusion properties to the secondsupport member in conjunction with the composite matrix.

The mesh may be a diamond shape mesh.

Alternatively, the mesh may be a chicken-wire style mesh (hexagonalmesh).

Other mesh shapes may be used without departing from the principles ofthe present invention.

In some embodiments the second support member may also be urgedoutwardly against the bore wall, in use, to help create a seal.

Suitable materials for the various components include, but are notlimited to elastomers such as nitrile, hydrogenated nitrile,fluoroelastomers, perfluoroelastomers, thermoplastic materials, EPDM,polyurethane, and the like for the flexible sealing element and/or thecomposite matrix; metals such as steel, brass, or the like, or polymericmaterials such as PEEK, nylon, Kevlar and/or metal fabrics or the likefor the first support member and/or the composite reinforcing material.

The second support member may be located adjacent the first supportmember at an outer portion of the flexible sealing element.

At least a portion of the second support member may extend radiallyinwards of the first support member.

The second support member may comprise a free end which is not bonded tothe flexible sealing element.

The second support member may comprise a free end and a bonded end,which is bonded to the flexible sealing element. The free end allowsmovement and expansion of the flexible sealing element relative to thesecond support member, while the bonded end serves to both retain thesecond support member in place relative to the flexible sealing element,and further reduces the risk of flow and/or extrusion of the flexiblesealing element.

The first support member may be located adjacent to the free end of thesecond support member. In at least one embodiment of the presentinvention this arrangement allows the combination of the first supportmember and the second support member to move relative to the flexiblesealing element when under pressure.

Preferably, the flexible sealing element is selectively bonded to thebody of the first and/or second support member.

A portion of the flexible sealing element may be bonded to a portion ofthe first support member and a further portion of the flexible sealingelement may be bonded to a portion of the second support member.

Any suitable means may be used to bond the components of the device; forexample, glue or other adhesive, welding, vulcanisation, heat treatment,mechanical fasteners, bonding agents, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described withreference to the accompanying drawings in which:

FIG. 1 is a section through a pressure control device for sealing anannulus between a mandrel and a wellbore, according to a firstembodiment of the present invention, the pressure control device shownin a run-in configuration;

FIG. 2 is a close-up of part of the pressure control device of FIG. 1 inthe run-in configuration;

FIG. 3 is a close-up of part of the pressure control device of FIG. 1 inthe set configuration;

FIG. 4 is a perspective view of a section of the deformable reinforcingelement, and

FIG. 4A shows a close-up of part of the section of the reinforcingelement.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to FIG. 1, a section through a pressure controldevice 10 for sealing an annulus 12 between a mandrel 14 and a wellbore16, according to a first embodiment of the present invention; thepressure control device 10 is shown in a run-in configuration. Thepressure control device 10 is a packer and comprises a flexible sealingelement 18 comprising an upper flexible sealing element portion 20, acentral flexible sealing element portion 22 and a lower flexible sealingelement portion 24. The central flexible sealing element portion 22 isseparated from the upper flexible sealing element 20 and the lowerflexible sealing element 24 by first and second seal rings 26, 28respectively. The sealing element portions 20, 22, 24 comprise anelastomer, particularly nitrile butadiene rubber.

The pressure control device 10 further comprises two first supportmembers 30, 32 and two second support members 34, 36. The structure andoperation of the first and second support members 30, 32, 34, 36 will bediscussed in due course.

The pressure control device 10 further comprises an upper setting disc38 and a lower setting disc 40, the discs 38, 40 being adapted to bemoved towards each other and move the sealing element portions 20, 22,24 from the run-in configuration shown in FIG. 1 to a set configurationshown in and discussed in connection with FIG. 3.

Referring to FIG. 2, which illustrates a close-up of part of thepressure control device 10 of FIG. 1 in the run-in configuration, thestructure of the first support members 30, 32 and the second supportmembers 34, 36 will be discussed with particular reference to the lowerpair of support members 32, 36.

The first support member 32 comprises a circular helical spring 42. Thehelical spring 42 rests on a cammed surface 44 defined by the lowersetting disc 40 and is embedded in the matrix 46 of a composite material48 which makes up the second support member 36.

The matrix 46 of the composite material 48 is an elastomer such asnitrile butadiene rubber and is reinforced by a deformable reinforcingelement 50.

FIG. 4 shows a perspective view of a section of the deformablereinforcing element 50 and FIG. 4A shows a close-up of part of thesection of the reinforcing element 50. The reinforcing element 50 isfrusto-conical in shape and is made from a length of steel mesh 52wrapped around a former (not shown) around forty to fifty times.

As can be seen from FIG. 4A, the steel mesh 52 defines voids 54. Betweenadjacent layers of mesh 52, there is partial but not complete alignmentof the voids 54 through the reinforcing element 50. The reason for thispartial alignment will now be discussed.

During manufacture of the second support member 36 the matrix material46 is adapted to permeate into the reinforcing element voids 54 as thereinforcing element 50 is embedded in the second support member 36 asthe second support member 36 is pressure formed around the reinforcingelement 50.

The pressure control device 10 is moved from the run-in configuration tothe set configuration by applying a force to the setting discs 38, 40 tomove the setting discs towards each other, compressing the flexiblesealing elements 20, 22, 24. Due to the presence of the mandrel 14, thesealing elements 20, 22, 24 can only expand radially outwardly andexpand into engagement with a wellbore wall 56 (best seen in FIG. 3, aclose-up of part of the pressure control device 10 of FIG. 1 in the setconfiguration).

In the set configuration, the flexible sealing portions 20, 22, 24 areengaged with the wellbore wall 56 and under pressure and temperature inthe wellbore 16 would be inclined to extrude into the gap indicated bythe letter “A” on FIG. 3.

As can be seen from FIG. 3, however, the first support member 32 hastravelled down the cammed surface 44 as the second seal element 24 iscompressed, to substantially fill the gap A. In addition, because thefirst support member 32 is substantially encased within the secondsupport member 36, the softer elastomer of the seal element 24 isprevented from seeping through the interface 60 between the firstsupport member 32 and the cammed surface 44 or the interface 62 betweenthe first support member 32 and the wellbore wall 56. The harderelastomer of the second support member 36 is selected so that seepagethrough the interfaces 60, 62 is negligible under normal operatingpressures.

Continuing to refer to FIG. 3, the second support member 36 also comesinto engagement with the wellbore wall 56 due to the reinforcing element50 deforming under the setting pressure.

As previously stated, the first support member 32 is in the form of ahelical spring 42. The spring 42 is biased to the run-in position and isin an expanded state in the set position. In the set position adjacentcoils will, therefore, be separated with a gap between. The use of aharder elastomer for the matrix 46 of the second support member 36 andthe presence of the reinforcing element 50 reduces seepage of the secondsupport member 36 into the gaps between the separated coils. This allowsthe first support member 32 to recover to the run-in configuration whenthe setting pressure is removed.

Various modifications and improvements may be made to theabove-described embodiments without departing from the scope of theinvention. For example, in low-temperature environments, a mechanicalforce could be applied to move the seal element to the sealed position.

Although the support element is shown as being a conical multilayer meshconstruction, other materials such as Kevlar could be used and othershapes such a cylindrical can be adopted.

Similarly, although the embodiments shown a packer type pressure controldevice, a further embodiment comprising a pressure control devicecomprising a flexible cup would also fall within the scope of theinvention.

1. A pressure control device for mounting on a mandrel, the devicecomprising: a flexible sealing element; a first support member; and asecond support member comprising a composite, wherein the pressurecontrol device is adapted to move from a run in position to an expandedposition when exposed to a source of pressure, the flexible sealingelement being adapted to form a seal against a bore wall in the expandedposition, the first and second support members being adapted, in theexpanded position, to resist extrusion of the flexible sealing element,in use, along the bore wall away from the source of pressure, the secondsupport member being further adapted to resist extrusion into the firstsupport member.
 2. A pressure control device according to claim 1wherein a portion of the flexible sealing element, the first supportmember and/or the second support member are arranged concentrically. 3.A pressure control device according to claim 1 wherein the first supportmember comprises a helical spring, the helical spring being biased tothe run-in position.
 4. (canceled)
 5. A pressure control deviceaccording to claim 1 wherein the first support member is located at anouter portion of the flexible sealing element.
 6. A pressure controldevice according to claim 1 wherein the first support member is urgedoutwardly against a bore wall, in use, to help to create a seal. 7.(canceled)
 8. (canceled)
 9. A pressure control device according to claim1 wherein the first support member comprises a circumferential firstspring with a second spring in its interior.
 10. A pressure controldevice according to claim 1 wherein the first support member comprises acircumferential first spring with a second spring in its interiorwherein the second spring is mounted within the first spring such thatthe helix of one spring is wound in the opposite direction to the spiralof the other spring in order to resist canting of the first supportmember under high pressure.
 11. A pressure control device according toclaim 1 wherein the first support member is located so as to abut thesecond support member.
 12. A pressure control device according to claim1 comprising a rigid body adapted for mounting on a mandrel or the like,the rigid body comprising an annular member, the first support memberbeing mounted to the annular member, the rigid body definging a cammedsurface adapted to be engaged by the first support member. 13.(canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled)
 17. (canceled)18. A pressure control device according to claim 1 wherein the firstsupport member is bonded to the second support member.
 19. A pressurecontrol device according to claim 1 wherein the first support member islocated on or adjacent the second support member.
 20. A pressure controldevice according to claim 1 wherein the second support member comprisesa composite of greater hardness than the flexible sealing elementlocated at an outer portion of the flexible sealing element.
 21. Apressure control device according to claim 1 wherein the composite ofthe second support member comprises a composite matrix and a reinforcingmaterial, the reinforcing material being more rigid than the compositematerial, the reinforcing material comprising a plurality of separatemembers, particles or fibres and a metal wire mesh.
 22. (canceled) 23.(canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)28. (canceled)
 29. A pressure control device according to claim 1wherein the second support member is urged outwardly against a borewall, in use, to help create a seal.
 30. A pressure control deviceaccording to claim 1 wherein the second support member is locatedadjacent the first support member at an outer portion of the flexiblesealing element.
 31. A pressure control device according to claim 1wherein at least a portion of the second support member extends radiallyinwards of the first support member.
 32. A pressure control deviceaccording to claim 1 wherein the second support member comprises a freeend which is not bonded to the flexible sealing element.
 33. A pressurecontrol device according to claim 1 wherein the second support membercomprises an end which is bonded to the flexible sealing element. 34.(canceled)
 35. A pressure control device according to claim 1 whereinthe flexible sealing element is selectively bonded to the body of thefirst and/or second support member.
 36. A pressure control deviceaccording to claim 1 wherein a portion of the flexible sealing elementis bonded to a portion of the first support member and a further portionof the flexible sealing element is bonded to a portion of the secondsupport member.